Sound is generated from a source producing audible waves transmitted outward from the source. A listener in a room with the source receives sound waves directly from the source or indirectly from sound waves being reflected from objects in the room or from the boundaries defining the room. The quality of sound may be altered, and may even be enhanced, by placing physical objects in the path of propagating sound waves. By absorbing, reflecting or diffusing sound waves, the quality of the sound can be enhanced. Absorption of sound waves occurs when a sound wave strikes a barrier that is capable of absorbing the energy of the sound wave. For example, absorption of energy of a sound wave is accomplished by placing in the path of the sound wave energy absorbing materials. For instance, insulation materials of various thicknesses, carpet, acoustic ceiling tile, draperies and other heavy fabrics will absorb energy from sound waves that strike these objects. By this absorption the sound wave will gradually lose energy. If a room is capable of totally absorbing sound then the room is described by the art as being dead. Ideally, a certain degree of energy or sound absorption is acceptable in a listening room to prevent formation .of standing waves. However, the listening room should not be so sound-absorptive that the room becomes dead, or that certain frequencies are lost due to absorption.
Reflection of sound waves occurs by changing the direction of a propagating energy wave without absorption. A hard surface, such as a drywall surface, wood, plaster or cement walls can function as devices for accomplishing reflection. The more dense the flat surfaces are the greater the ability of the surface to reflect sound. A certain amount of sound reflection is also considered desirable for listeners.
Diffusion, which is somewhat more complex than reflection or refraction, is a combination of reflection and refraction of the sound wave at the same time. That is, different segments or different frequencies emanating from a sound source when diffused will be delayed in time due to scattering or reflection of the wave. A sound source generally emits more than a single sound frequency. In diffusion, the different frequencies are reflected and scattered so that different frequencies are delayed in time. By provision of diffusion in a small recording studio, sounds in the studio can be perceived by the listener as being like those associated with a larger room, because the listener is exposed to the reflected, scattered and time delayed sound waves. Diffusor panels, used in the art, generally provide a means for achieving at least one dimensional sound diffusion, i.e., reflection and refraction in one direction.
The two main functional attributes of a diffusor are its spatial response and its temporal response. By design, a diffusor panel can have a defined spatial response, and this response can be represented on a polar response graph. The spatial response represents sound distribution and scattering, and is dependent upon the particular sound frequencies involved. Temporal response is defined as a reaction in time to an impulse. That is, as sound travels into a diffusor panel, any cavities in the diffusor panel cause time delays due to the differing depths of the panel. Total bandwidth of a diffusor panel is defined as the range of frequencies of sound in which the diffusor panel is effective in producing a spatial and temporal response. The temporal response may be defined as the difference between a monitored reflected sound and a monitored diffused sound.
Generally, prior devices have been made of panels with cavities. When used in a sound recording studio, a diffusor will be contacted by propagating sound waves. The sound waves will then be reflected and refracted at different time intervals because of the cavities of the diffusor. In the past, diffusion has been accomplished in a number of ways. Irregular shapes of differing depths have been created by the use of dimensional lumber, stone and brickwork. Diffusors made from these materials are usually custom made and engineered for the space to be affected. Usually, such devices are very costly, requiring many hours of time and expensive materials to produce.
One commercially available device, believed to be that disclosed in U.S. Deign Pat. No. 306,764, accomplishes diffusion by creating wells of equal width separated by dividers. The diffusors are wall- or ceiling-mounted, depending on their intended application or the desired result. However, the dividers used in this device are quite thin and when exposed to low frequencies, the diffusor will function more as a resonator (and, therefore, more as an absorber of sound energy) than a diffusor. This undesirable phenomenon occurs because the dividers do not possess a substantial mass. The dividers also prevent construction of a diffusor having wells of differing width.